The invention relates to Tape Automated Bonding (TAB) of semiconductor devices. Reference can be made to U.S. Pat. No. 4,234,666 for a basic teaching of TAB. In a copending patent application Ser. No. 138,030 filed Apr. 7, 1980, now abandoned in favor of continuation application Ser. No. 407,515 filed Aug. 12, 1982, and titled LEAD DESIGN FOR SEMICONDUCTOR AUTOMATIC ASSEMBLY, by Carmen D. Burns, a bonding tape is disclosed having integral strain relief elements useful in thermocompression (TC) bonding. The teachings in the above references are incorporated herein by reference.
Basically, in the single layer tape version of TAB a metal tape is provided with at least one row (and preferably two rows) of indexing and transport locater holes. A series of personality windows is formed in the tape in registry with the locater holes. Each personality window is provided with a metal finger pattern that extends from the edge of the personality window inwardly to a central array that is designed to mate with the bonding pad pattern on a particular semiconductor device, such as an IC chip or other electronic element. The tape is passed through an automated machine which bonds the tape fingers to an IC chip which then becomes attached to the tape, preferably by means of TC gang bonding.
The IC chip with the attached metal fingers can be subsequently excised from the tape and bonded to a secondary structure for further packaging such as mounting directly upon a printed wiring board or encapsulation in a dual in-line package (DIP) or other housing. This latter approach usually involves mounting a chip frame attached fingers upon a more substantial lead frame which employs a lead array that can ultimately be plugged into a DIP socket or mounted in suitable holes in a printed wiring board.
As pointed out above, the assembly tape is first run through an automatic machine which bonds an IC chip to each of the tape finger arrays. This is referred to as inner lead bond (ILB) formation. In this operation a thermode presses the inner ends of the metal tape fingers to the bonding pads on the chip so as to TC gang bond the tape fingers. In this operation, the tape is passed under a tape guide shoe which holds the tape in a controlled spatial location. This shoe is shaped so that the tape flexes as it passes through the machine. Such flexing can act to displace elements in the tape finger arrays and can act to cause a bonded chip to be deflected from its intended path. The bonded chip can, if deflected, come into contact with other yet to be bonded chips located in the machine and fracturing can occur. In fully automated equipment image processing is employed to evaluate the finger pattern and to align it with the semiconductor device bonding pads. If a lead is bent its optical reflection can be altered so that the image processing is incorrect. It has been found that the automated equipment can confuse a bent lead with a missing finger and thereby reject the assembly tape.